What makes a Venice core A64 run Pifast quiker than an Opteron?

[Zak33]

Hi guys,

We MA_rlins (IL-2 Squadron) have recently been debating (at some volume) the reasons behind something odd.

I have an Asus A8N-E mobo (nforce4 non sli) and with an Opteron 146 running at 10x250 HTT at 4x and 4x512 mb ddr at Cas2.5 2T (or even with 2x512ddr Cas2.5 and 1T ) I struggle to get my Pifast below 50 seconds.

If I crank it to 2.9, which it will do, I can get the thing under 50 seconds.

However, Yamangman has a Gigabyte mobo (no idea of model) with a Venice 3000+ at 2.5 and he runs sub 40 seconds.

And this week, I helped Dakaras to build a PC with an Abit KN8 SLi, and we put a 3200+ venice in, and when he cranked it to 2.5ghz he go Pifast of 41.29

So: What has changed on the memory controller or the cpu die to make it so much faster in this single test?

My cpu runs rock solid at 2.6 all day, at default volts, and in everything else it's like lightning, but in this one test it will not go faster with clock speed. Does my CPU clock speed vary without my knowledge? It's been suggested by brains far greater than mine, that I may need a few extra fractions of volts though that cpu, incase I'm suffering loss of Processor power?

I don't pertain to understand that, in fact I dfon't know if the word pertain is correct but I must admit that with this cpu, after 6 hours solid gaming, with no a whisper of a slow down in games or a crash, is it possible that I need a slightly higher potential difference across those little gaps?

[chuckskull]

Do opties have all the extra instructions like SSE and so on? I'm guessing a server chip doesn't need a lot of the multimedia ones and may bot be included?

[Zak33]

good question, but I think they do. Opty's are pretty well loaded. But I don't know for sure, so we'll await some uber brains to answer

I ....as is well known....do not have an uber brain

[Lee H]

Are the memory timings for both systems the same as this could have an effect on the performance overall?

The Standard AN8 uses the Nforce4 chipset whereas the KN8 uses the Nforce4 Ultra chipset. Maybe subtle changes within these 2 varients of the chipsets are affecting the results as well. You can see the differences between the nforce4 and nforce4 ultra chipsets at the link Here but the only differences really are in the networking and support for SATA300 drives on the controller

I reckon it's down to memory timings myself but I expect someone here to come and blow me away with another theory very shortly

[Max Tractor]

Opterons are just the same as other a64 cpu's, difference between venice/opteron 512/1m l2 cache, same as a san diego, but the 939 opterons are opterons because they are binned for the server market, less volts/better silicon.

What is your super pi 1m time? Tight timings/1t will make a difference

[Max Tractor]

Just ran it on my

opteron 146@2.5/2x512-2.5-3-3-7 1T 166 divider 208mhz/250htt = 48.47 ------Super Pi 1m 33.906

opteron 146@2.5/2x512-2.5-4-4-8 1T 1:1 250mhz/250htt...........= 47.94 ------Super Pi 1m 33.407


going to run it on my venice and 144


Opteron 144@2.7/2x256 2-3-3-6 1T 133 Divder 193mhz/300htt.......=Series Computing time - 37.25
...........................................................................................=Division Time - 4.55
...........................................................................................=Invsqrt - 2.80
...........................................................................................=Final muti time - 1.91
...........................................................................................= = 46.63 --------Super Pi 1m 32.735



Venice 3200@2.7/2X1024GB 2.5-4-4-7 1T 166 Divider 225mhz/270htt - 45.91

Venice 3200@2.5/2X1024GB 2.5-4-4-7 1T 166 Divider 208mhz/250htt = 49.45

[toolsong]

Opt 146@2.6 = 32s

Super Pi v1.1e, 1M calculations

RAM is 1T 3-3-2-8 at 1:1 260HTT

[Max Tractor]

Opt 146@2.6 = 32s

How so fast? This is pifast, right? This is the first time I have ran this app, the total time we are interested in here?

[Zak33]

ya see....people get totally different scores and I'm sure my timings are dead similar to Dak's.

I'm gonna tweak my timings a tad and see what improvements I get.

Lee....this A8N-E does have the Ultra chipset. I checked

[chuckskull]

Post a CPU-z screenie zak, should be easy to spot anything unusual from their.

[Max Tractor]

There is nothing wrong with my systems, there must be tweaks for this program

[toolsong]

How so fast? This is pifast, right? This is the first time I have ran this app, the total time we are interested in here?

Sorry was Super Pi, close to your scores

Have updated post

[Zak33]

just for clarity it's Hexus Pifast we're using

http://pifast.hexus.net/pifast.php

download from there

[chuckskull]

i think most of this comes from confusing pifast with superpi

[Max Tractor]

Opteron 146/144 added veince

[Zak33]

thanks Tractor. Those times are very similar to mine too on the Opty.

Weird huh? I know two people with Venice's going waaay quicker.